Donald sells 760 marbles every day. he sells each marble for 1.5 dollars.
for how many days does donald need to sell marbles to earn 3420 dollars?

Well, let's see. First we would need to find how much money he earns each DAY. To find THAT, we would need to multiply 760 times 1.5, which would be $1,140. Now, in order to find out how many DAYS it will take to make $3,420, you would divide 3,420 divided by 1,140, which will be 3. So it will take 3 days to earn $3,420.
I hope I helped! =D

Just a second zzz